After water reaches its boiling point, it becomes moist steam that is a mixture of water vapor gas (the gas phase part) and water droplets (the liquid phase part). Here the weight ratio of the water vapor gas relative to the moist steam is termed the “dryness fraction.” For example, if water vapor gas and water droplets exist at half each, then the dryness fraction would be 0.5. Moreover, when there are no water droplets but instead there is only water vapor gas, then the dryness fraction would be 1.0. From the perspective of efficiency of use of the apparent heat and latent heat within the moist steam in heat exchanging equipment, and the like, from the perspective of preventing corrosion of turbine blades in steam turbines, and so forth, it is desirable that the dryness fraction of the moist steam be brought to near 1.0. Because of this, a variety of methods have been proposed whereby to measure the moist steam. For example, Japanese Unexamined Patent Application Publication H8-312908 (the JP '908) discloses a technology for calculating the dryness fraction by calculating the saturated hydraulic enthalpy and the saturated steam enthalpy using a saturated steam table based on the dry steam flow rates and pressures before and after a pressure regulating valve, taking advantage of the fact that there is no change in total enthalpy across a pressure regulating valve that is disposed in a pipe.
However, in the technology disclosed in the JP '908, it is necessary to cause the moist steam that is to be measured to undergo a state change from the two-phase state to the gas phase state, and also necessary to stabilize, in the gas phase state, that which is to be measured, and thus there is a problem in that measuring the dryness fraction is time-consuming. Moreover, the technology disclosed in the JP '908 is unable to measure the distribution of the dryness fraction within the moist steam.
Given this, one aspect of the present disclosure is the provision of a dryness fraction distribution measuring device and dryness fraction distribution measuring method whereby the dryness fraction distribution can be measured accurately and easily.